Sites: GlobalSpec.com | GlobalSpec Electronics | CR4 | Electronics360
Login | Register
The Engineer's Place for News and Discussion®

Previous in Forum: Electrical Network Configuration.....   Next in Forum: lossing phase
Close

Comments Format:






Close

Subscribe to Discussion:

CR4 allows you to "subscribe" to a discussion
so that you can be notified of new comments to
the discussion via email.

Close

Rating Vote:







2 comments
Anonymous Poster

ABB SPAJ140C --- CT RATIO CONFUSION

10/25/2009 11:07 AM

I am using ABB SPAJ140C Over current protection relay for the transformer feeder 630KVA,13.8KV / 220-127V.

The Current drawn at primary is 15 ampere.

The CT ratio is 100 / 5 Amp.

The overcurrent unit of SPCJ 4D29 of ABB SPAJ140C unit; the low set over current stage I > at definite time characteristic is 0.5 --- 5.0 X In ( Where the rated current in my case is 5 Amp ).

To protect the transformer on overcurrent, if it is above 20 Ampere; what setting I have to choose to acivate my protection relay to trip.

0.5 setting belong to 10 Ampere or 50 Ampere ?

1.0 setting belong to 20 Ampere or 100 Ampere ?

Reply
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.
Member

Join Date: Oct 2009
Posts: 5
#1

Re: ABB SPAJ140C --- CT RATIO CONFUSION

10/25/2009 1:56 PM

your transformer is 630kva,13.8kv

I=630/13.8*1.73=630/23.87=26.39A

the current = 26.40A

C.T ratio = 100/5=20

relay current=26.40/20=1.32A

with spaj relay you can chose In = 1 or = 5

we chose In=1

set the relay = 1.32

1.32*1=1.32

hope it is correct

Reply
Anonymous Poster
#2

Re: ABB SPAJ140C --- CT RATIO CONFUSION

10/25/2009 10:52 PM

for CT ratio of 100/5 or 100/1, if the setting is 0.5 it is 50 amps on primary.if the setting is 1, the primary current is 100 Amps.

Reply
Reply to Forum Thread 2 comments
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.

Previous in Forum: Electrical Network Configuration.....   Next in Forum: lossing phase
You might be interested in: Masters and Setting Gages, Current Sense Amplifiers, Current Transformers